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	$161.78	4.191%	$168.5602	$168.56	$168.55	$168.60
Purchase #2	$209.37	6.804%	$223.6155	$223.62	$223.60	$223.60
Purchase #3	$87.73	4.488%	$91.6673	$91.67	$91.65	$91.70
Purchase #4	$210.95	13.820%	$240.1033	$240.10	$240.10	$240.10
Purchase #5	$99.89	6.837%	$106.7195	$106.72	$106.70	$106.70
Purchase #6	$110.79	7.188%	$118.7536	$118.75	$118.75	$118.80
Purchase #7	$131.73	10.569%	$145.6525	$145.65	$145.65	$145.70
7 purchase totals =	$1,012.24		$1,095.0719	$1,095.07	$1,095.00	$1,095.20