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	$183.61	6.847%	$196.1818	$196.18	$196.20	$196.20
Purchase #2	$196.97	6.162%	$209.1073	$209.11	$209.10	$209.10
Purchase #3	$211.72	11.530%	$236.1313	$236.13	$236.15	$236.10
Purchase #4	$104.55	3.543%	$108.2542	$108.25	$108.25	$108.30
Purchase #5	$244.72	7.686%	$263.5292	$263.53	$263.55	$263.50
Purchase #6	$63.96	11.459%	$71.2892	$71.29	$71.30	$71.30
Purchase #7	$176.72	6.407%	$188.0425	$188.04	$188.05	$188.00
7 purchase totals =	$1,182.25		$1,272.5355	$1,272.53	$1,272.60	$1,272.50