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	$146.98	12.873%	$165.9007	$165.90	$165.90	$165.90
Purchase #2	$153.84	8.222%	$166.4887	$166.49	$166.50	$166.50
Purchase #3	$16.31	13.619%	$18.5313	$18.53	$18.55	$18.50
Purchase #4	$196.55	13.342%	$222.7737	$222.77	$222.75	$222.80
Purchase #5	$212.44	3.586%	$220.0581	$220.06	$220.05	$220.10
Purchase #6	$142.61	9.669%	$156.399	$156.40	$156.40	$156.40
Purchase #7	$136.28	5.502%	$143.7781	$143.78	$143.80	$143.80
7 purchase totals =	$1,005.01		$1,093.9296	$1,093.93	$1,093.95	$1,094.00