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	$136.70	7.863%	$147.4487	$147.45	$147.45	$147.40
Purchase #2	$198.90	5.701%	$210.2393	$210.24	$210.25	$210.20
Purchase #3	$181.44	8.335%	$196.563	$196.56	$196.55	$196.60
Purchase #4	$204.32	8.459%	$221.6034	$221.60	$221.60	$221.60
Purchase #5	$238.31	8.176%	$257.7942	$257.79	$257.80	$257.80
Purchase #6	$110.84	11.340%	$123.4093	$123.41	$123.40	$123.40
Purchase #7	$101.74	3.311%	$105.1086	$105.11	$105.10	$105.10
7 purchase totals =	$1,172.25		$1,262.1665	$1,262.16	$1,262.15	$1,262.10