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	$159.64	5.524%	$168.4585	$168.46	$168.45	$168.50
Purchase #2	$235.84	7.136%	$252.6695	$252.67	$252.65	$252.70
Purchase #3	$31.81	4.527%	$33.25	$33.25	$33.25	$33.30
Purchase #4	$6.79	3.109%	$7.0011	$7.00	$7.00	$7.00
Purchase #5	$174.72	12.635%	$196.7959	$196.80	$196.80	$196.80
Purchase #6	$244.72	10.348%	$270.0436	$270.04	$270.05	$270.00
Purchase #7	$93.38	11.674%	$104.2812	$104.28	$104.30	$104.30
7 purchase totals =	$946.90		$1,032.4998	$1,032.50	$1,032.50	$1,032.60