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	$187.62	11.624%	$209.4289	$209.43	$209.45	$209.40
Purchase #2	$24.46	4.177%	$25.4817	$25.48	$25.50	$25.50
Purchase #3	$174.51	10.490%	$192.8161	$192.82	$192.80	$192.80
Purchase #4	$168.65	11.399%	$187.8744	$187.87	$187.85	$187.90
Purchase #5	$155.82	6.190%	$165.4653	$165.47	$165.45	$165.50
Purchase #6	$149.78	13.260%	$169.6408	$169.64	$169.65	$169.60
Purchase #7	$39.88	9.614%	$43.7141	$43.71	$43.70	$43.70
7 purchase totals =	$900.72		$994.4213	$994.42	$994.40	$994.40