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	$84.70	4.686%	$88.669	$88.67	$88.65	$88.70
Purchase #2	$172.98	13.570%	$196.4534	$196.45	$196.45	$196.50
Purchase #3	$47.43	10.119%	$52.2294	$52.23	$52.25	$52.20
Purchase #4	$79.30	11.210%	$88.1895	$88.19	$88.20	$88.20
Purchase #5	$135.93	4.506%	$142.055	$142.06	$142.05	$142.10
Purchase #6	$18.79	8.366%	$20.362	$20.36	$20.35	$20.40
Purchase #7	$97.85	13.720%	$111.275	$111.28	$111.30	$111.30
7 purchase totals =	$636.98		$699.2333	$699.24	$699.25	$699.40