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	$129.70	8.372%	$140.5585	$140.56	$140.55	$140.60
Purchase #2	$101.91	9.242%	$111.3285	$111.33	$111.35	$111.30
Purchase #3	$179.46	6.811%	$191.683	$191.68	$191.70	$191.70
Purchase #4	$79.50	4.571%	$83.1339	$83.13	$83.15	$83.10
Purchase #5	$37.29	8.216%	$40.3537	$40.35	$40.35	$40.40
Purchase #6	$178.29	10.218%	$196.5077	$196.51	$196.50	$196.50
Purchase #7	$232.27	11.634%	$259.2923	$259.29	$259.30	$259.30
7 purchase totals =	$938.42		$1,022.8576	$1,022.85	$1,022.90	$1,022.90