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	$173.80	4.652%	$181.8852	$181.89	$181.90	$181.90
Purchase #2	$231.99	3.641%	$240.4368	$240.44	$240.45	$240.40
Purchase #3	$39.25	7.293%	$42.1125	$42.11	$42.10	$42.10
Purchase #4	$186.95	10.629%	$206.8209	$206.82	$206.80	$206.80
Purchase #5	$216.42	3.222%	$223.3931	$223.39	$223.40	$223.40
Purchase #6	$178.30	4.666%	$186.6195	$186.62	$186.60	$186.60
Purchase #7	$64.74	6.647%	$69.0433	$69.04	$69.05	$69.00
7 purchase totals =	$1,091.45		$1,150.3113	$1,150.31	$1,150.30	$1,150.20