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	$31.89	10.409%	$35.2094	$35.21	$35.20	$35.20
Purchase #2	$148.56	3.769%	$154.1592	$154.16	$154.15	$154.20
Purchase #3	$178.91	4.431%	$186.8375	$186.84	$186.85	$186.80
Purchase #4	$186.53	5.313%	$196.4403	$196.44	$196.45	$196.40
Purchase #5	$61.92	5.208%	$65.1448	$65.14	$65.15	$65.10
Purchase #6	$85.75	6.474%	$91.3015	$91.30	$91.30	$91.30
Purchase #7	$63.83	13.794%	$72.6347	$72.63	$72.65	$72.60
7 purchase totals =	$757.39		$801.7274	$801.72	$801.75	$801.60