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	$35.97	4.530%	$37.5994	$37.60	$37.60	$37.60
Purchase #2	$136.30	9.374%	$149.0768	$149.08	$149.10	$149.10
Purchase #3	$148.51	9.809%	$163.0773	$163.08	$163.10	$163.10
Purchase #4	$62.59	4.408%	$65.349	$65.35	$65.35	$65.30
Purchase #5	$85.72	4.615%	$89.676	$89.68	$89.70	$89.70
Purchase #6	$25.85	11.731%	$28.8825	$28.88	$28.90	$28.90
Purchase #7	$75.83	8.651%	$82.3901	$82.39	$82.40	$82.40
7 purchase totals =	$570.77		$616.0511	$616.06	$616.15	$616.10