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	$26.51	6.799%	$28.3124	$28.31	$28.30	$28.30
Purchase #2	$232.60	4.485%	$243.0321	$243.03	$243.05	$243.00
Purchase #3	$224.73	10.365%	$248.0233	$248.02	$248.00	$248.00
Purchase #4	$66.72	8.108%	$72.1297	$72.13	$72.15	$72.10
Purchase #5	$162.32	11.612%	$181.1686	$181.17	$181.15	$181.20
Purchase #6	$143.57	7.280%	$154.0219	$154.02	$154.00	$154.00
Purchase #7	$73.83	11.215%	$82.11	$82.11	$82.10	$82.10
7 purchase totals =	$930.28		$1,008.7980	$1,008.79	$1,008.75	$1,008.70