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	$180.98	5.436%	$190.8181	$190.82	$190.80	$190.80
Purchase #2	$54.82	11.474%	$61.11	$61.11	$61.10	$61.10
Purchase #3	$168.44	10.852%	$186.7191	$186.72	$186.70	$186.70
Purchase #4	$49.83	5.496%	$52.5687	$52.57	$52.55	$52.60
Purchase #5	$151.53	3.350%	$156.6063	$156.61	$156.60	$156.60
Purchase #6	$154.62	12.766%	$174.3588	$174.36	$174.35	$174.40
Purchase #7	$199.79	5.477%	$210.7325	$210.73	$210.75	$210.70
7 purchase totals =	$960.01		$1,032.9135	$1,032.92	$1,032.85	$1,032.90