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	$223.55	6.585%	$238.2708	$238.27	$238.25	$238.30
Purchase #2	$90.28	11.478%	$100.6423	$100.64	$100.65	$100.60
Purchase #3	$8.74	5.483%	$9.2192	$9.22	$9.20	$9.20
Purchase #4	$132.87	7.532%	$142.8778	$142.88	$142.90	$142.90
Purchase #5	$72.46	12.217%	$81.3124	$81.31	$81.30	$81.30
Purchase #6	$235.39	6.325%	$250.2784	$250.28	$250.30	$250.30
Purchase #7	$227.32	12.705%	$256.201	$256.20	$256.20	$256.20
7 purchase totals =	$990.61		$1,078.8019	$1,078.80	$1,078.80	$1,078.80