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	$116.32	12.130%	$130.4296	$130.43	$130.45	$130.40
Purchase #2	$168.70	7.454%	$181.2749	$181.27	$181.25	$181.30
Purchase #3	$125.35	13.472%	$142.2372	$142.24	$142.25	$142.20
Purchase #4	$193.52	6.403%	$205.9111	$205.91	$205.90	$205.90
Purchase #5	$178.94	9.596%	$196.1111	$196.11	$196.10	$196.10
Purchase #6	$231.33	7.533%	$248.7561	$248.76	$248.75	$248.80
Purchase #7	$70.82	13.844%	$80.6243	$80.62	$80.60	$80.60
7 purchase totals =	$1,084.98		$1,185.3443	$1,185.34	$1,185.30	$1,185.30