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	$113.86	11.721%	$127.2055	$127.21	$127.20	$127.20
Purchase #2	$106.97	6.698%	$114.1349	$114.13	$114.15	$114.10
Purchase #3	$215.38	11.396%	$239.9247	$239.92	$239.90	$239.90
Purchase #4	$137.77	7.266%	$147.7804	$147.78	$147.80	$147.80
Purchase #5	$229.58	4.404%	$239.6907	$239.69	$239.70	$239.70
Purchase #6	$156.39	12.183%	$175.443	$175.44	$175.45	$175.40
Purchase #7	$59.38	3.777%	$61.6228	$61.62	$61.60	$61.60
7 purchase totals =	$1,019.33		$1,105.8020	$1,105.79	$1,105.80	$1,105.70