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	$182.94	3.507%	$189.3557	$189.36	$189.35	$189.40
Purchase #2	$70.96	12.318%	$79.7009	$79.70	$79.70	$79.70
Purchase #3	$219.55	8.131%	$237.4016	$237.40	$237.40	$237.40
Purchase #4	$70.27	12.255%	$78.8816	$78.88	$78.90	$78.90
Purchase #5	$233.48	4.460%	$243.8932	$243.89	$243.90	$243.90
Purchase #6	$168.49	11.243%	$187.4333	$187.43	$187.45	$187.40
Purchase #7	$53.77	3.278%	$55.5326	$55.53	$55.55	$55.50
7 purchase totals =	$999.46		$1,072.1989	$1,072.19	$1,072.25	$1,072.20