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	$92.97	11.750%	$103.894	$103.89	$103.90	$103.90
Purchase #2	$89.78	7.482%	$96.4973	$96.50	$96.50	$96.50
Purchase #3	$136.32	11.595%	$152.1263	$152.13	$152.15	$152.10
Purchase #4	$250.33	4.140%	$260.6937	$260.69	$260.70	$260.70
Purchase #5	$211.31	4.352%	$220.5062	$220.51	$220.50	$220.50
Purchase #6	$160.94	12.503%	$181.0623	$181.06	$181.05	$181.10
Purchase #7	$229.99	10.713%	$254.6288	$254.63	$254.65	$254.60
7 purchase totals =	$1,171.64		$1,269.4086	$1,269.41	$1,269.45	$1,269.40