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	$144.77	12.362%	$162.6665	$162.67	$162.65	$162.70
Purchase #2	$149.65	8.436%	$162.2745	$162.27	$162.25	$162.30
Purchase #3	$72.61	13.154%	$82.1611	$82.16	$82.15	$82.20
Purchase #4	$250.55	7.872%	$270.2733	$270.27	$270.25	$270.30
Purchase #5	$47.44	5.638%	$50.1147	$50.11	$50.10	$50.10
Purchase #6	$220.81	7.234%	$236.7834	$236.78	$236.80	$236.80
Purchase #7	$83.39	13.487%	$94.6368	$94.64	$94.65	$94.60
7 purchase totals =	$969.22		$1,058.9103	$1,058.90	$1,058.85	$1,059.00