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	$73.44	12.250%	$82.4364	$82.44	$82.45	$82.40
Purchase #2	$231.28	12.624%	$260.4768	$260.48	$260.50	$260.50
Purchase #3	$152.59	10.509%	$168.6257	$168.63	$168.65	$168.60
Purchase #4	$227.41	8.254%	$246.1804	$246.18	$246.20	$246.20
Purchase #5	$19.93	3.169%	$20.5616	$20.56	$20.55	$20.60
Purchase #6	$91.55	5.668%	$96.7391	$96.74	$96.75	$96.70
Purchase #7	$141.83	3.846%	$147.2848	$147.28	$147.30	$147.30
7 purchase totals =	$938.03		$1,022.3048	$1,022.31	$1,022.40	$1,022.30