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	$180.29	10.138%	$198.5678	$198.57	$198.55	$198.60
Purchase #2	$147.29	10.204%	$162.3195	$162.32	$162.30	$162.30
Purchase #3	$28.93	8.416%	$31.3647	$31.36	$31.35	$31.40
Purchase #4	$155.56	7.378%	$167.0372	$167.04	$167.05	$167.00
Purchase #5	$106.41	4.467%	$111.1633	$111.16	$111.15	$111.20
Purchase #6	$64.89	6.736%	$69.261	$69.26	$69.25	$69.30
Purchase #7	$56.96	8.527%	$61.817	$61.82	$61.80	$61.80
7 purchase totals =	$740.33		$801.5305	$801.53	$801.45	$801.60