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	$191.92	7.497%	$206.3082	$206.31	$206.30	$206.30
Purchase #2	$18.79	3.124%	$19.377	$19.38	$19.40	$19.40
Purchase #3	$133.35	4.543%	$139.4081	$139.41	$139.40	$139.40
Purchase #4	$30.37	8.869%	$33.0635	$33.06	$33.05	$33.10
Purchase #5	$218.72	3.866%	$227.1757	$227.18	$227.20	$227.20
Purchase #6	$191.47	4.722%	$200.5112	$200.51	$200.50	$200.50
Purchase #7	$49.34	8.356%	$53.4629	$53.46	$53.45	$53.50
7 purchase totals =	$833.96		$879.3066	$879.31	$879.30	$879.40