Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.33	7.198%	$174.0145	$174.01	$174.00	$174.00
Purchase #2	$167.25	10.647%	$185.0571	$185.06	$185.05	$185.10
Purchase #3	$143.86	12.325%	$161.5907	$161.59	$161.60	$161.60
Purchase #4	$147.42	8.757%	$160.3296	$160.33	$160.35	$160.30
Purchase #5	$191.44	13.659%	$217.5888	$217.59	$217.60	$217.60
Purchase #6	$211.95	5.371%	$223.3338	$223.33	$223.35	$223.30
Purchase #7	$159.79	4.230%	$166.5491	$166.55	$166.55	$166.50
7 purchase totals =	$1,184.04		$1,288.4636	$1,288.46	$1,288.50	$1,288.40