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	$143.78	4.119%	$149.7023	$149.70	$149.70	$149.70
Purchase #2	$183.77	4.134%	$191.3671	$191.37	$191.35	$191.40
Purchase #3	$24.36	13.333%	$27.6079	$27.61	$27.60	$27.60
Purchase #4	$57.70	7.579%	$62.0731	$62.07	$62.05	$62.10
Purchase #5	$73.59	6.134%	$78.104	$78.10	$78.10	$78.10
Purchase #6	$106.79	10.789%	$118.3116	$118.31	$118.30	$118.30
Purchase #7	$60.63	10.117%	$66.7639	$66.76	$66.75	$66.80
7 purchase totals =	$650.62		$693.9299	$693.92	$693.85	$694.00