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	$103.58	6.625%	$110.4422	$110.44	$110.45	$110.40
Purchase #2	$98.86	12.725%	$111.4399	$111.44	$111.45	$111.40
Purchase #3	$18.53	9.755%	$20.3376	$20.34	$20.35	$20.30
Purchase #4	$56.81	9.412%	$62.157	$62.16	$62.15	$62.20
Purchase #5	$50.97	5.612%	$53.8304	$53.83	$53.85	$53.80
Purchase #6	$138.97	12.865%	$156.8485	$156.85	$156.85	$156.80
Purchase #7	$162.61	13.694%	$184.8778	$184.88	$184.90	$184.90
7 purchase totals =	$630.33		$699.9334	$699.94	$700.00	$699.80