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	$85.56	13.140%	$96.8026	$96.80	$96.80	$96.80
Purchase #2	$15.25	13.593%	$17.3229	$17.32	$17.30	$17.30
Purchase #3	$72.91	13.216%	$82.5458	$82.55	$82.55	$82.50
Purchase #4	$42.84	7.689%	$46.134	$46.13	$46.15	$46.10
Purchase #5	$99.68	12.575%	$112.2148	$112.21	$112.20	$112.20
Purchase #6	$186.79	7.451%	$200.7077	$200.71	$200.70	$200.70
Purchase #7	$52.31	4.276%	$54.5468	$54.55	$54.55	$54.50
7 purchase totals =	$555.34		$610.2746	$610.27	$610.25	$610.10