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	$173.55	5.350%	$182.8349	$182.83	$182.85	$182.80
Purchase #2	$106.36	4.799%	$111.4642	$111.46	$111.45	$111.50
Purchase #3	$185.78	13.208%	$210.3178	$210.32	$210.30	$210.30
Purchase #4	$191.59	7.563%	$206.08	$206.08	$206.10	$206.10
Purchase #5	$231.33	5.598%	$244.2799	$244.28	$244.30	$244.30
Purchase #6	$138.78	4.596%	$145.1583	$145.16	$145.15	$145.20
Purchase #7	$171.76	3.808%	$178.3006	$178.30	$178.30	$178.30
7 purchase totals =	$1,199.15		$1,278.4357	$1,278.43	$1,278.45	$1,278.50