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	$174.59	7.430%	$187.562	$187.56	$187.55	$187.60
Purchase #2	$91.59	12.107%	$102.6788	$102.68	$102.70	$102.70
Purchase #3	$133.40	9.799%	$146.4719	$146.47	$146.45	$146.50
Purchase #4	$149.72	9.769%	$164.3461	$164.35	$164.35	$164.30
Purchase #5	$198.89	5.238%	$209.3079	$209.31	$209.30	$209.30
Purchase #6	$245.74	6.556%	$261.8507	$261.85	$261.85	$261.90
Purchase #7	$164.96	9.623%	$180.8341	$180.83	$180.85	$180.80
7 purchase totals =	$1,158.89		$1,253.0515	$1,253.05	$1,253.05	$1,253.10