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	$89.69	5.218%	$94.37	$94.37	$94.35	$94.40
Purchase #2	$162.36	6.479%	$172.8793	$172.88	$172.90	$172.90
Purchase #3	$182.32	6.515%	$194.1981	$194.20	$194.20	$194.20
Purchase #4	$115.47	4.103%	$120.2077	$120.21	$120.20	$120.20
Purchase #5	$203.91	11.550%	$227.4616	$227.46	$227.45	$227.50
Purchase #6	$152.65	6.653%	$162.8058	$162.81	$162.80	$162.80
Purchase #7	$94.90	11.240%	$105.5668	$105.57	$105.55	$105.60
7 purchase totals =	$1,001.30		$1,077.4893	$1,077.50	$1,077.45	$1,077.60