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	$36.49	11.149%	$40.5583	$40.56	$40.55	$40.60
Purchase #2	$175.32	6.528%	$186.7649	$186.76	$186.75	$186.80
Purchase #3	$214.65	4.589%	$224.5003	$224.50	$224.50	$224.50
Purchase #4	$113.33	12.263%	$127.2277	$127.23	$127.25	$127.20
Purchase #5	$97.78	9.584%	$107.1512	$107.15	$107.15	$107.20
Purchase #6	$223.69	10.259%	$246.6384	$246.64	$246.65	$246.60
Purchase #7	$209.50	6.386%	$222.8787	$222.88	$222.90	$222.90
7 purchase totals =	$1,070.76		$1,155.7195	$1,155.72	$1,155.75	$1,155.80