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	$34.33	7.671%	$36.9635	$36.96	$36.95	$37.00
Purchase #2	$215.86	3.222%	$222.815	$222.82	$222.80	$222.80
Purchase #3	$144.40	5.144%	$151.8279	$151.83	$151.85	$151.80
Purchase #4	$241.80	11.637%	$269.9383	$269.94	$269.95	$269.90
Purchase #5	$134.79	5.185%	$141.7789	$141.78	$141.80	$141.80
Purchase #6	$167.42	6.812%	$178.8247	$178.82	$178.80	$178.80
Purchase #7	$86.91	5.458%	$91.6535	$91.65	$91.65	$91.70
7 purchase totals =	$1,025.51		$1,093.8018	$1,093.80	$1,093.80	$1,093.80