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	$93.27	8.208%	$100.9256	$100.93	$100.95	$100.90
Purchase #2	$120.81	7.540%	$129.9191	$129.92	$129.90	$129.90
Purchase #3	$31.94	5.174%	$33.5926	$33.59	$33.60	$33.60
Purchase #4	$233.34	9.268%	$254.966	$254.97	$254.95	$255.00
Purchase #5	$188.72	12.745%	$212.7724	$212.77	$212.75	$212.80
Purchase #6	$49.31	8.394%	$53.4491	$53.45	$53.45	$53.40
Purchase #7	$156.77	7.172%	$168.0135	$168.01	$168.00	$168.00
7 purchase totals =	$874.16		$953.6383	$953.64	$953.60	$953.60