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	$104.54	12.208%	$117.3022	$117.30	$117.30	$117.30
Purchase #2	$99.46	12.399%	$111.792	$111.79	$111.80	$111.80
Purchase #3	$80.31	6.337%	$85.3992	$85.40	$85.40	$85.40
Purchase #4	$180.31	13.774%	$205.1459	$205.15	$205.15	$205.10
Purchase #5	$224.46	10.825%	$248.7578	$248.76	$248.75	$248.80
Purchase #6	$137.29	7.170%	$147.1337	$147.13	$147.15	$147.10
Purchase #7	$98.69	8.597%	$107.1744	$107.17	$107.15	$107.20
7 purchase totals =	$925.06		$1,022.7052	$1,022.70	$1,022.70	$1,022.70