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	$124.33	8.235%	$134.5686	$134.57	$134.55	$134.60
Purchase #2	$244.50	10.582%	$270.373	$270.37	$270.35	$270.40
Purchase #3	$50.89	4.328%	$53.0925	$53.09	$53.10	$53.10
Purchase #4	$16.99	9.450%	$18.5956	$18.60	$18.60	$18.60
Purchase #5	$232.61	13.816%	$264.7474	$264.75	$264.75	$264.70
Purchase #6	$185.56	10.645%	$205.3129	$205.31	$205.30	$205.30
Purchase #7	$52.87	4.514%	$55.2566	$55.26	$55.25	$55.30
7 purchase totals =	$907.75		$1,001.9466	$1,001.95	$1,001.90	$1,002.00