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	$96.92	4.368%	$101.1535	$101.15	$101.15	$101.20
Purchase #2	$112.81	10.353%	$124.4892	$124.49	$124.50	$124.50
Purchase #3	$234.67	10.413%	$259.1062	$259.11	$259.10	$259.10
Purchase #4	$142.61	3.471%	$147.56	$147.56	$147.55	$147.60
Purchase #5	$89.46	7.672%	$96.3234	$96.32	$96.30	$96.30
Purchase #6	$156.83	11.337%	$174.6098	$174.61	$174.60	$174.60
Purchase #7	$126.30	12.311%	$141.8488	$141.85	$141.85	$141.80
7 purchase totals =	$959.60		$1,045.0909	$1,045.09	$1,045.05	$1,045.10