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	$242.65	8.788%	$263.9741	$263.97	$263.95	$264.00
Purchase #2	$33.48	5.743%	$35.4028	$35.40	$35.40	$35.40
Purchase #3	$215.96	9.151%	$235.7225	$235.72	$235.70	$235.70
Purchase #4	$36.33	13.576%	$41.2622	$41.26	$41.25	$41.30
Purchase #5	$178.82	9.753%	$196.2603	$196.26	$196.25	$196.30
Purchase #6	$90.52	6.850%	$96.7206	$96.72	$96.70	$96.70
Purchase #7	$228.33	3.411%	$236.1183	$236.12	$236.10	$236.10
7 purchase totals =	$1,026.09		$1,105.4608	$1,105.45	$1,105.35	$1,105.50