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	$173.44	6.737%	$185.1247	$185.12	$185.10	$185.10
Purchase #2	$182.40	9.855%	$200.3755	$200.38	$200.40	$200.40
Purchase #3	$229.36	11.711%	$256.2203	$256.22	$256.20	$256.20
Purchase #4	$133.27	13.394%	$151.1202	$151.12	$151.10	$151.10
Purchase #5	$81.88	7.701%	$88.1856	$88.19	$88.20	$88.20
Purchase #6	$200.88	3.491%	$207.8927	$207.89	$207.90	$207.90
Purchase #7	$172.41	11.341%	$191.963	$191.96	$191.95	$192.00
7 purchase totals =	$1,173.64		$1,280.8820	$1,280.88	$1,280.85	$1,280.90