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	$219.75	6.217%	$233.4119	$233.41	$233.40	$233.40
Purchase #2	$241.61	3.217%	$249.3826	$249.38	$249.40	$249.40
Purchase #3	$189.76	11.146%	$210.9106	$210.91	$210.90	$210.90
Purchase #4	$164.43	12.736%	$185.3718	$185.37	$185.35	$185.40
Purchase #5	$162.27	8.805%	$176.5579	$176.56	$176.55	$176.60
Purchase #6	$102.94	6.635%	$109.7701	$109.77	$109.75	$109.80
Purchase #7	$39.68	10.176%	$43.7178	$43.72	$43.70	$43.70
7 purchase totals =	$1,120.44		$1,209.1227	$1,209.12	$1,209.05	$1,209.20