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	$29.91	7.406%	$32.1251	$32.13	$32.15	$32.10
Purchase #2	$218.30	9.565%	$239.1804	$239.18	$239.20	$239.20
Purchase #3	$164.89	11.840%	$184.413	$184.41	$184.40	$184.40
Purchase #4	$171.62	3.873%	$178.2668	$178.27	$178.25	$178.30
Purchase #5	$19.94	13.280%	$22.588	$22.59	$22.60	$22.60
Purchase #6	$155.97	12.730%	$175.825	$175.83	$175.85	$175.80
Purchase #7	$220.70	3.815%	$229.1197	$229.12	$229.10	$229.10
7 purchase totals =	$981.33		$1,061.5180	$1,061.53	$1,061.55	$1,061.50