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	$124.49	8.818%	$135.4675	$135.47	$135.45	$135.50
Purchase #2	$90.46	13.871%	$103.0077	$103.01	$103.00	$103.00
Purchase #3	$118.84	7.154%	$127.3418	$127.34	$127.35	$127.30
Purchase #4	$99.33	12.322%	$111.5694	$111.57	$111.55	$111.60
Purchase #5	$185.98	7.383%	$199.7109	$199.71	$199.70	$199.70
Purchase #6	$71.69	8.681%	$77.9134	$77.91	$77.90	$77.90
Purchase #7	$239.37	7.199%	$256.6022	$256.60	$256.60	$256.60
7 purchase totals =	$930.16		$1,011.6129	$1,011.61	$1,011.55	$1,011.60