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	$38.82	7.393%	$41.69	$41.69	$41.70	$41.70
Purchase #2	$65.48	7.711%	$70.5292	$70.53	$70.55	$70.50
Purchase #3	$244.45	13.535%	$277.5363	$277.54	$277.55	$277.50
Purchase #4	$102.39	10.679%	$113.3242	$113.32	$113.30	$113.30
Purchase #5	$161.55	4.556%	$168.9102	$168.91	$168.90	$168.90
Purchase #6	$110.40	9.111%	$120.4585	$120.46	$120.45	$120.50
Purchase #7	$67.53	6.755%	$72.0917	$72.09	$72.10	$72.10
7 purchase totals =	$790.62		$864.5401	$864.54	$864.55	$864.50