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	$149.68	4.266%	$156.0653	$156.07	$156.05	$156.10
Purchase #2	$50.25	10.142%	$55.3464	$55.35	$55.35	$55.30
Purchase #3	$64.68	12.491%	$72.7592	$72.76	$72.75	$72.80
Purchase #4	$165.33	3.681%	$171.4158	$171.42	$171.40	$171.40
Purchase #5	$106.67	3.135%	$110.0141	$110.01	$110.00	$110.00
Purchase #6	$16.72	11.165%	$18.5868	$18.59	$18.60	$18.60
Purchase #7	$154.47	12.731%	$174.1356	$174.14	$174.15	$174.10
7 purchase totals =	$707.80		$758.3232	$758.34	$758.30	$758.30