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	$101.65	7.295%	$109.0654	$109.07	$109.05	$109.10
Purchase #2	$120.69	5.446%	$127.2628	$127.26	$127.25	$127.30
Purchase #3	$200.56	5.636%	$211.8636	$211.86	$211.85	$211.90
Purchase #4	$121.82	6.806%	$130.1111	$130.11	$130.10	$130.10
Purchase #5	$205.49	9.416%	$224.8389	$224.84	$224.85	$224.80
Purchase #6	$109.92	3.837%	$114.1376	$114.14	$114.15	$114.10
Purchase #7	$99.84	5.825%	$105.6557	$105.66	$105.65	$105.70
7 purchase totals =	$959.97		$1,022.9351	$1,022.94	$1,022.90	$1,023.00