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	$203.42	3.352%	$210.2386	$210.24	$210.25	$210.20
Purchase #2	$174.70	6.189%	$185.5122	$185.51	$185.50	$185.50
Purchase #3	$105.86	4.221%	$110.3284	$110.33	$110.35	$110.30
Purchase #4	$101.34	3.581%	$104.969	$104.97	$104.95	$105.00
Purchase #5	$85.39	4.334%	$89.0908	$89.09	$89.10	$89.10
Purchase #6	$239.44	3.761%	$248.4453	$248.45	$248.45	$248.40
Purchase #7	$64.91	11.235%	$72.2026	$72.20	$72.20	$72.20
7 purchase totals =	$975.06		$1,020.7869	$1,020.79	$1,020.80	$1,020.70