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	$77.92	9.629%	$85.4229	$85.42	$85.40	$85.40
Purchase #2	$213.65	4.745%	$223.7877	$223.79	$223.80	$223.80
Purchase #3	$110.53	6.367%	$117.5674	$117.57	$117.55	$117.60
Purchase #4	$141.78	7.813%	$152.8573	$152.86	$152.85	$152.90
Purchase #5	$135.53	13.319%	$153.5812	$153.58	$153.60	$153.60
Purchase #6	$35.76	5.853%	$37.853	$37.85	$37.85	$37.90
Purchase #7	$234.77	6.783%	$250.6944	$250.69	$250.70	$250.70
7 purchase totals =	$949.94		$1,021.7639	$1,021.76	$1,021.75	$1,021.90