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	$186.72	13.335%	$211.6191	$211.62	$211.60	$211.60
Purchase #2	$69.89	10.689%	$77.3605	$77.36	$77.35	$77.40
Purchase #3	$31.95	4.794%	$33.4817	$33.48	$33.50	$33.50
Purchase #4	$89.61	7.661%	$96.475	$96.48	$96.50	$96.50
Purchase #5	$107.84	5.831%	$114.1282	$114.13	$114.15	$114.10
Purchase #6	$144.78	5.238%	$152.3636	$152.36	$152.35	$152.40
Purchase #7	$225.40	13.437%	$255.687	$255.69	$255.70	$255.70
7 purchase totals =	$856.19		$941.1151	$941.12	$941.15	$941.20