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	$85.44	13.312%	$96.8138	$96.81	$96.80	$96.80
Purchase #2	$227.64	9.254%	$248.7058	$248.71	$248.70	$248.70
Purchase #3	$79.89	11.740%	$89.2691	$89.27	$89.25	$89.30
Purchase #4	$184.40	6.370%	$196.1463	$196.15	$196.15	$196.10
Purchase #5	$20.93	5.200%	$22.0184	$22.02	$22.00	$22.00
Purchase #6	$157.29	12.132%	$176.3724	$176.37	$176.35	$176.40
Purchase #7	$220.61	7.506%	$237.169	$237.17	$237.15	$237.20
7 purchase totals =	$976.20		$1,066.4948	$1,066.50	$1,066.40	$1,066.50