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	$152.41	3.582%	$157.8693	$157.87	$157.85	$157.90
Purchase #2	$148.42	4.656%	$155.3304	$155.33	$155.35	$155.30
Purchase #3	$77.27	6.204%	$82.0638	$82.06	$82.05	$82.10
Purchase #4	$91.60	7.414%	$98.3912	$98.39	$98.40	$98.40
Purchase #5	$30.30	8.599%	$32.9055	$32.91	$32.90	$32.90
Purchase #6	$46.32	3.199%	$47.8018	$47.80	$47.80	$47.80
Purchase #7	$76.32	11.589%	$85.1647	$85.16	$85.15	$85.20
7 purchase totals =	$622.64		$659.5267	$659.52	$659.50	$659.60