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	$89.88	4.745%	$94.1448	$94.14	$94.15	$94.10
Purchase #2	$89.54	13.818%	$101.9126	$101.91	$101.90	$101.90
Purchase #3	$238.77	6.157%	$253.4711	$253.47	$253.45	$253.50
Purchase #4	$88.65	4.499%	$92.6384	$92.64	$92.65	$92.60
Purchase #5	$214.25	7.311%	$229.9138	$229.91	$229.90	$229.90
Purchase #6	$172.91	10.150%	$190.4604	$190.46	$190.45	$190.50
Purchase #7	$247.48	9.109%	$270.023	$270.02	$270.00	$270.00
7 purchase totals =	$1,141.48		$1,232.5641	$1,232.55	$1,232.50	$1,232.50