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	$144.96	4.342%	$151.2542	$151.25	$151.25	$151.30
Purchase #2	$117.28	13.667%	$133.3087	$133.31	$133.30	$133.30
Purchase #3	$248.39	6.390%	$264.2621	$264.26	$264.25	$264.30
Purchase #4	$115.97	12.454%	$130.4129	$130.41	$130.40	$130.40
Purchase #5	$196.42	11.830%	$219.6565	$219.66	$219.65	$219.70
Purchase #6	$75.25	6.869%	$80.4189	$80.42	$80.40	$80.40
Purchase #7	$139.89	6.150%	$148.4932	$148.49	$148.50	$148.50
7 purchase totals =	$1,038.16		$1,127.8065	$1,127.80	$1,127.75	$1,127.90