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	$135.79	7.607%	$146.1195	$146.12	$146.10	$146.10
Purchase #2	$58.55	4.641%	$61.2673	$61.27	$61.25	$61.30
Purchase #3	$134.86	5.579%	$142.3838	$142.38	$142.40	$142.40
Purchase #4	$175.66	4.123%	$182.9025	$182.90	$182.90	$182.90
Purchase #5	$84.98	5.839%	$89.942	$89.94	$89.95	$89.90
Purchase #6	$78.69	11.483%	$87.726	$87.73	$87.75	$87.70
Purchase #7	$143.72	4.599%	$150.3297	$150.33	$150.35	$150.30
7 purchase totals =	$812.25		$860.6708	$860.67	$860.70	$860.60