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	$90.72	6.778%	$96.869	$96.87	$96.85	$96.90
Purchase #2	$39.68	13.493%	$45.034	$45.03	$45.05	$45.00
Purchase #3	$110.35	7.726%	$118.8756	$118.88	$118.90	$118.90
Purchase #4	$31.33	7.753%	$33.759	$33.76	$33.75	$33.80
Purchase #5	$12.32	3.682%	$12.7736	$12.77	$12.75	$12.80
Purchase #6	$52.26	11.609%	$58.3269	$58.33	$58.35	$58.30
Purchase #7	$217.46	3.582%	$225.2494	$225.25	$225.25	$225.20
7 purchase totals =	$554.12		$590.8875	$590.89	$590.90	$590.90