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	$75.93	11.402%	$84.5875	$84.59	$84.60	$84.60
Purchase #2	$33.57	11.831%	$37.5417	$37.54	$37.55	$37.50
Purchase #3	$92.49	6.438%	$98.4445	$98.44	$98.45	$98.40
Purchase #4	$169.43	13.141%	$191.6948	$191.69	$191.70	$191.70
Purchase #5	$220.33	4.225%	$229.6389	$229.64	$229.65	$229.60
Purchase #6	$100.62	13.461%	$114.1645	$114.16	$114.15	$114.20
Purchase #7	$93.32	12.847%	$105.3088	$105.31	$105.30	$105.30
7 purchase totals =	$785.69		$861.3807	$861.37	$861.40	$861.30