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	$128.26	10.614%	$141.8735	$141.87	$141.85	$141.90
Purchase #2	$168.30	3.781%	$174.6634	$174.66	$174.65	$174.70
Purchase #3	$51.95	10.749%	$57.5341	$57.53	$57.55	$57.50
Purchase #4	$141.41	4.193%	$147.3393	$147.34	$147.35	$147.30
Purchase #5	$229.71	11.818%	$256.8571	$256.86	$256.85	$256.90
Purchase #6	$42.87	6.419%	$45.6218	$45.62	$45.60	$45.60
Purchase #7	$174.48	8.311%	$188.981	$188.98	$189.00	$189.00
7 purchase totals =	$936.98		$1,012.8702	$1,012.86	$1,012.85	$1,012.90