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	$147.96	5.753%	$156.4721	$156.47	$156.45	$156.50
Purchase #2	$14.59	13.761%	$16.5977	$16.60	$16.60	$16.60
Purchase #3	$17.32	7.132%	$18.5553	$18.56	$18.55	$18.60
Purchase #4	$81.54	5.196%	$85.7768	$85.78	$85.80	$85.80
Purchase #5	$220.72	11.137%	$245.3016	$245.30	$245.30	$245.30
Purchase #6	$153.42	11.461%	$171.0035	$171.00	$171.00	$171.00
Purchase #7	$53.80	12.780%	$60.6756	$60.68	$60.70	$60.70
7 purchase totals =	$689.35		$754.3826	$754.39	$754.40	$754.50