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	$240.73	5.102%	$253.012	$253.01	$253.00	$253.00
Purchase #2	$160.35	9.774%	$176.0226	$176.02	$176.00	$176.00
Purchase #3	$55.66	7.770%	$59.9848	$59.98	$60.00	$60.00
Purchase #4	$56.49	5.481%	$59.5862	$59.59	$59.60	$59.60
Purchase #5	$48.38	3.561%	$50.1028	$50.10	$50.10	$50.10
Purchase #6	$166.41	4.784%	$174.3711	$174.37	$174.35	$174.40
Purchase #7	$158.85	13.624%	$180.4917	$180.49	$180.50	$180.50
7 purchase totals =	$886.87		$953.5712	$953.56	$953.55	$953.60