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	$127.34	11.600%	$142.1114	$142.11	$142.10	$142.10
Purchase #2	$91.98	6.679%	$98.1233	$98.12	$98.10	$98.10
Purchase #3	$94.40	7.692%	$101.6612	$101.66	$101.65	$101.70
Purchase #4	$116.48	3.603%	$120.6768	$120.68	$120.70	$120.70
Purchase #5	$175.37	9.205%	$191.5128	$191.51	$191.50	$191.50
Purchase #6	$180.98	12.776%	$204.102	$204.10	$204.10	$204.10
Purchase #7	$222.88	13.519%	$253.0111	$253.01	$253.00	$253.00
7 purchase totals =	$1,009.43		$1,111.1986	$1,111.19	$1,111.15	$1,111.20