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	$79.44	13.632%	$90.2693	$90.27	$90.25	$90.30
Purchase #2	$189.58	12.323%	$212.9419	$212.94	$212.95	$212.90
Purchase #3	$39.46	6.747%	$42.1224	$42.12	$42.10	$42.10
Purchase #4	$87.90	8.425%	$95.3056	$95.31	$95.30	$95.30
Purchase #5	$191.55	7.140%	$205.2267	$205.23	$205.25	$205.20
Purchase #6	$171.30	12.186%	$192.1746	$192.17	$192.15	$192.20
Purchase #7	$89.39	5.614%	$94.4084	$94.41	$94.40	$94.40
7 purchase totals =	$848.62		$932.4489	$932.45	$932.40	$932.40