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	$78.57	5.756%	$83.0925	$83.09	$83.10	$83.10
Purchase #2	$35.98	4.467%	$37.5872	$37.59	$37.60	$37.60
Purchase #3	$249.35	5.769%	$263.735	$263.74	$263.75	$263.70
Purchase #4	$229.53	9.410%	$251.1288	$251.13	$251.15	$251.10
Purchase #5	$75.33	6.405%	$80.1549	$80.15	$80.15	$80.20
Purchase #6	$169.95	9.627%	$186.3111	$186.31	$186.30	$186.30
Purchase #7	$139.43	9.361%	$152.482	$152.48	$152.50	$152.50
7 purchase totals =	$978.14		$1,054.4915	$1,054.49	$1,054.55	$1,054.50