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	$119.57	7.600%	$128.6573	$128.66	$128.65	$128.70
Purchase #2	$68.45	6.377%	$72.8151	$72.82	$72.80	$72.80
Purchase #3	$109.32	5.234%	$115.0418	$115.04	$115.05	$115.00
Purchase #4	$14.84	13.586%	$16.8562	$16.86	$16.85	$16.90
Purchase #5	$211.90	10.301%	$233.7278	$233.73	$233.75	$233.70
Purchase #6	$231.86	12.276%	$260.3231	$260.32	$260.30	$260.30
Purchase #7	$246.33	7.346%	$264.4254	$264.43	$264.45	$264.40
7 purchase totals =	$1,002.27		$1,091.8467	$1,091.86	$1,091.85	$1,091.80