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	$127.33	4.851%	$133.5068	$133.51	$133.50	$133.50
Purchase #2	$129.60	3.439%	$134.0569	$134.06	$134.05	$134.10
Purchase #3	$101.31	4.346%	$105.7129	$105.71	$105.70	$105.70
Purchase #4	$189.85	3.269%	$196.0562	$196.06	$196.05	$196.10
Purchase #5	$219.31	8.796%	$238.6005	$238.60	$238.60	$238.60
Purchase #6	$85.90	7.381%	$92.2403	$92.24	$92.25	$92.20
Purchase #7	$209.43	9.423%	$229.1646	$229.16	$229.15	$229.20
7 purchase totals =	$1,062.73		$1,129.3382	$1,129.34	$1,129.30	$1,129.40