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	$224.87	13.763%	$255.8189	$255.82	$255.80	$255.80
Purchase #2	$170.61	9.449%	$186.7309	$186.73	$186.75	$186.70
Purchase #3	$73.69	13.649%	$83.7479	$83.75	$83.75	$83.70
Purchase #4	$90.25	3.145%	$93.0884	$93.09	$93.10	$93.10
Purchase #5	$218.57	3.131%	$225.4134	$225.41	$225.40	$225.40
Purchase #6	$165.45	11.658%	$184.7382	$184.74	$184.75	$184.70
Purchase #7	$71.94	9.521%	$78.7894	$78.79	$78.80	$78.80
7 purchase totals =	$1,015.38		$1,108.3271	$1,108.33	$1,108.35	$1,108.20