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	$79.64	11.161%	$88.5286	$88.53	$88.55	$88.50
Purchase #2	$20.50	4.595%	$21.442	$21.44	$21.45	$21.40
Purchase #3	$67.30	6.694%	$71.8051	$71.81	$71.80	$71.80
Purchase #4	$94.87	6.335%	$100.88	$100.88	$100.90	$100.90
Purchase #5	$33.36	11.280%	$37.123	$37.12	$37.10	$37.10
Purchase #6	$98.48	6.418%	$104.8004	$104.80	$104.80	$104.80
Purchase #7	$219.41	4.701%	$229.7245	$229.72	$229.70	$229.70
7 purchase totals =	$613.56		$654.3036	$654.30	$654.30	$654.20