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	$148.32	9.415%	$162.2843	$162.28	$162.30	$162.30
Purchase #2	$153.84	11.162%	$171.0116	$171.01	$171.00	$171.00
Purchase #3	$93.91	9.632%	$102.9554	$102.96	$102.95	$103.00
Purchase #4	$43.27	6.861%	$46.2388	$46.24	$46.25	$46.20
Purchase #5	$100.28	4.747%	$105.0403	$105.04	$105.05	$105.00
Purchase #6	$136.74	9.775%	$150.1063	$150.11	$150.10	$150.10
Purchase #7	$147.86	12.154%	$165.8309	$165.83	$165.85	$165.80
7 purchase totals =	$824.22		$903.4676	$903.47	$903.50	$903.40