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	$41.91	4.191%	$43.6664	$43.67	$43.65	$43.70
Purchase #2	$205.48	8.262%	$222.4568	$222.46	$222.45	$222.50
Purchase #3	$180.31	13.203%	$204.1163	$204.12	$204.10	$204.10
Purchase #4	$165.25	13.349%	$187.3092	$187.31	$187.30	$187.30
Purchase #5	$223.25	8.368%	$241.9316	$241.93	$241.95	$241.90
Purchase #6	$18.40	13.793%	$20.9379	$20.94	$20.95	$20.90
Purchase #7	$89.82	11.256%	$99.9301	$99.93	$99.95	$99.90
7 purchase totals =	$924.42		$1,020.3483	$1,020.36	$1,020.35	$1,020.30