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	$91.88	4.380%	$95.9043	$95.90	$95.90	$95.90
Purchase #2	$213.79	3.765%	$221.8392	$221.84	$221.85	$221.80
Purchase #3	$247.98	9.789%	$272.2548	$272.25	$272.25	$272.30
Purchase #4	$6.32	8.754%	$6.8733	$6.87	$6.85	$6.90
Purchase #5	$173.56	11.801%	$194.0418	$194.04	$194.05	$194.00
Purchase #6	$123.31	4.132%	$128.4052	$128.41	$128.40	$128.40
Purchase #7	$88.30	3.222%	$91.145	$91.15	$91.15	$91.10
7 purchase totals =	$945.14		$1,010.4636	$1,010.46	$1,010.45	$1,010.40