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	$235.62	3.252%	$243.2824	$243.28	$243.30	$243.30
Purchase #2	$145.33	4.519%	$151.8975	$151.90	$151.90	$151.90
Purchase #3	$235.42	3.412%	$243.4525	$243.45	$243.45	$243.50
Purchase #4	$242.63	13.672%	$275.8024	$275.80	$275.80	$275.80
Purchase #5	$198.61	3.445%	$205.4521	$205.45	$205.45	$205.50
Purchase #6	$165.26	9.597%	$181.12	$181.12	$181.10	$181.10
Purchase #7	$56.99	4.356%	$59.4725	$59.47	$59.45	$59.50
7 purchase totals =	$1,279.86		$1,360.4794	$1,360.47	$1,360.45	$1,360.60