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	$148.52	11.338%	$165.3592	$165.36	$165.35	$165.40
Purchase #2	$212.33	3.763%	$220.32	$220.32	$220.30	$220.30
Purchase #3	$103.50	11.521%	$115.4242	$115.42	$115.40	$115.40
Purchase #4	$147.89	4.415%	$154.4193	$154.42	$154.40	$154.40
Purchase #5	$56.50	13.539%	$64.1495	$64.15	$64.15	$64.10
Purchase #6	$116.55	9.854%	$128.0348	$128.03	$128.05	$128.00
Purchase #7	$242.31	3.400%	$250.5485	$250.55	$250.55	$250.50
7 purchase totals =	$1,027.60		$1,098.2555	$1,098.25	$1,098.20	$1,098.10