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	$23.74	5.737%	$25.102	$25.10	$25.10	$25.10
Purchase #2	$96.77	11.166%	$107.5753	$107.58	$107.60	$107.60
Purchase #3	$181.66	13.742%	$206.6237	$206.62	$206.60	$206.60
Purchase #4	$74.41	5.256%	$78.321	$78.32	$78.30	$78.30
Purchase #5	$95.78	4.219%	$99.821	$99.82	$99.80	$99.80
Purchase #6	$79.46	13.478%	$90.1696	$90.17	$90.15	$90.20
Purchase #7	$107.91	11.681%	$120.515	$120.52	$120.50	$120.50
7 purchase totals =	$659.73		$728.1276	$728.13	$728.05	$728.10