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	$185.59	13.432%	$210.5184	$210.52	$210.50	$210.50
Purchase #2	$202.49	13.143%	$229.1033	$229.10	$229.10	$229.10
Purchase #3	$118.59	7.566%	$127.5625	$127.56	$127.55	$127.60
Purchase #4	$83.32	10.477%	$92.0494	$92.05	$92.05	$92.00
Purchase #5	$106.97	12.312%	$120.1401	$120.14	$120.15	$120.10
Purchase #6	$226.65	4.718%	$237.3433	$237.34	$237.35	$237.30
Purchase #7	$136.70	10.695%	$151.3201	$151.32	$151.30	$151.30
7 purchase totals =	$1,060.31		$1,168.0371	$1,168.03	$1,168.00	$1,167.90