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	$166.40	4.790%	$174.3706	$174.37	$174.35	$174.40
Purchase #2	$26.34	13.433%	$29.8783	$29.88	$29.90	$29.90
Purchase #3	$170.59	7.300%	$183.0431	$183.04	$183.05	$183.00
Purchase #4	$100.27	6.301%	$106.588	$106.59	$106.60	$106.60
Purchase #5	$170.81	8.543%	$185.4023	$185.40	$185.40	$185.40
Purchase #6	$244.93	8.118%	$264.8134	$264.81	$264.80	$264.80
Purchase #7	$50.92	13.421%	$57.754	$57.75	$57.75	$57.80
7 purchase totals =	$930.26		$1,001.8497	$1,001.84	$1,001.85	$1,001.90