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	$151.43	7.139%	$162.2406	$162.24	$162.25	$162.20
Purchase #2	$120.69	6.280%	$128.2693	$128.27	$128.25	$128.30
Purchase #3	$105.44	11.762%	$117.8419	$117.84	$117.85	$117.80
Purchase #4	$35.74	5.391%	$37.6667	$37.67	$37.65	$37.70
Purchase #5	$85.92	5.562%	$90.6989	$90.70	$90.70	$90.70
Purchase #6	$218.43	6.132%	$231.8241	$231.82	$231.80	$231.80
Purchase #7	$142.29	4.512%	$148.7101	$148.71	$148.70	$148.70
7 purchase totals =	$859.94		$917.2516	$917.25	$917.20	$917.20