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	$64.28	11.428%	$71.6259	$71.63	$71.65	$71.60
Purchase #2	$130.94	12.666%	$147.5249	$147.52	$147.50	$147.50
Purchase #3	$182.68	9.710%	$200.4182	$200.42	$200.40	$200.40
Purchase #4	$217.92	3.270%	$225.046	$225.05	$225.05	$225.00
Purchase #5	$39.31	5.593%	$41.5086	$41.51	$41.50	$41.50
Purchase #6	$55.54	6.818%	$59.3267	$59.33	$59.35	$59.30
Purchase #7	$196.51	12.543%	$221.1582	$221.16	$221.15	$221.20
7 purchase totals =	$887.18		$966.6085	$966.62	$966.60	$966.50