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	$92.39	4.761%	$96.7887	$96.79	$96.80	$96.80
Purchase #2	$197.78	3.163%	$204.0358	$204.04	$204.05	$204.00
Purchase #3	$38.48	11.473%	$42.8948	$42.89	$42.90	$42.90
Purchase #4	$65.76	11.564%	$73.3645	$73.36	$73.35	$73.40
Purchase #5	$64.41	3.348%	$66.5664	$66.57	$66.55	$66.60
Purchase #6	$79.78	13.417%	$90.4841	$90.48	$90.50	$90.50
Purchase #7	$139.68	9.475%	$152.9147	$152.91	$152.90	$152.90
7 purchase totals =	$678.28		$727.0490	$727.04	$727.05	$727.10