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	$23.79	8.554%	$25.825	$25.83	$25.85	$25.80
Purchase #2	$224.91	6.809%	$240.2241	$240.22	$240.20	$240.20
Purchase #3	$157.34	6.126%	$166.9786	$166.98	$167.00	$167.00
Purchase #4	$240.74	6.503%	$256.3953	$256.40	$256.40	$256.40
Purchase #5	$150.82	9.516%	$165.172	$165.17	$165.15	$165.20
Purchase #6	$86.27	3.607%	$89.3818	$89.38	$89.40	$89.40
Purchase #7	$222.63	3.479%	$230.3753	$230.38	$230.40	$230.40
7 purchase totals =	$1,106.50		$1,174.3521	$1,174.36	$1,174.40	$1,174.40