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	$160.30	13.608%	$182.1136	$182.11	$182.10	$182.10
Purchase #2	$144.28	3.789%	$149.7468	$149.75	$149.75	$149.70
Purchase #3	$115.44	10.452%	$127.5058	$127.51	$127.50	$127.50
Purchase #4	$86.34	7.705%	$92.9925	$92.99	$93.00	$93.00
Purchase #5	$55.89	6.523%	$59.5357	$59.54	$59.55	$59.50
Purchase #6	$49.71	6.196%	$52.79	$52.79	$52.80	$52.80
Purchase #7	$81.58	9.521%	$89.3472	$89.35	$89.35	$89.30
7 purchase totals =	$693.54		$754.0316	$754.04	$754.05	$753.90