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	$172.53	11.240%	$191.9224	$191.92	$191.90	$191.90
Purchase #2	$181.75	11.426%	$202.5168	$202.52	$202.50	$202.50
Purchase #3	$127.69	12.257%	$143.341	$143.34	$143.35	$143.30
Purchase #4	$247.27	9.354%	$270.3996	$270.40	$270.40	$270.40
Purchase #5	$82.71	4.560%	$86.4816	$86.48	$86.50	$86.50
Purchase #6	$212.56	4.595%	$222.3271	$222.33	$222.35	$222.30
Purchase #7	$45.37	13.436%	$51.4659	$51.47	$51.45	$51.50
7 purchase totals =	$1,069.88		$1,168.4544	$1,168.46	$1,168.45	$1,168.40