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	$130.29	6.818%	$139.1732	$139.17	$139.15	$139.20
Purchase #2	$229.58	5.501%	$242.2092	$242.21	$242.20	$242.20
Purchase #3	$50.58	4.609%	$52.9112	$52.91	$52.90	$52.90
Purchase #4	$129.61	5.545%	$136.7969	$136.80	$136.80	$136.80
Purchase #5	$216.83	6.676%	$231.3056	$231.31	$231.30	$231.30
Purchase #6	$161.43	8.645%	$175.3856	$175.39	$175.40	$175.40
Purchase #7	$128.66	3.786%	$133.5311	$133.53	$133.55	$133.50
7 purchase totals =	$1,046.98		$1,111.3128	$1,111.32	$1,111.30	$1,111.30