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	$168.87	13.658%	$191.9343	$191.93	$191.95	$191.90
Purchase #2	$168.83	13.298%	$191.281	$191.28	$191.30	$191.30
Purchase #3	$157.67	7.503%	$169.5	$169.50	$169.50	$169.50
Purchase #4	$143.77	9.489%	$157.4123	$157.41	$157.40	$157.40
Purchase #5	$49.28	12.328%	$55.3552	$55.36	$55.35	$55.40
Purchase #6	$189.54	11.522%	$211.3788	$211.38	$211.40	$211.40
Purchase #7	$38.52	8.763%	$41.8955	$41.90	$41.90	$41.90
7 purchase totals =	$916.48		$1,018.7571	$1,018.76	$1,018.80	$1,018.80