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	$13.29	7.377%	$14.2704	$14.27	$14.25	$14.30
Purchase #2	$9.56	8.788%	$10.4001	$10.40	$10.40	$10.40
Purchase #3	$149.53	7.321%	$160.4771	$160.48	$160.50	$160.50
Purchase #4	$86.52	4.185%	$90.1409	$90.14	$90.15	$90.10
Purchase #5	$67.77	4.851%	$71.0575	$71.06	$71.05	$71.10
Purchase #6	$109.52	8.316%	$118.6277	$118.63	$118.65	$118.60
Purchase #7	$76.46	3.738%	$79.3181	$79.32	$79.30	$79.30
7 purchase totals =	$512.65		$544.2918	$544.30	$544.30	$544.30