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	$35.28	5.224%	$37.123	$37.12	$37.10	$37.10
Purchase #2	$115.59	8.581%	$125.5088	$125.51	$125.50	$125.50
Purchase #3	$33.36	12.687%	$37.5924	$37.59	$37.60	$37.60
Purchase #4	$88.46	12.871%	$99.8457	$99.85	$99.85	$99.80
Purchase #5	$27.51	6.632%	$29.3345	$29.33	$29.35	$29.30
Purchase #6	$200.76	8.540%	$217.9049	$217.90	$217.90	$217.90
Purchase #7	$168.89	7.135%	$180.9403	$180.94	$180.95	$180.90
7 purchase totals =	$669.85		$728.2496	$728.24	$728.25	$728.10