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	$55.63	6.585%	$59.2932	$59.29	$59.30	$59.30
Purchase #2	$239.54	12.340%	$269.0992	$269.10	$269.10	$269.10
Purchase #3	$215.27	4.108%	$224.1133	$224.11	$224.10	$224.10
Purchase #4	$141.58	6.192%	$150.3466	$150.35	$150.35	$150.30
Purchase #5	$136.31	12.174%	$152.9044	$152.90	$152.90	$152.90
Purchase #6	$212.86	7.476%	$228.7734	$228.77	$228.75	$228.80
Purchase #7	$27.26	10.427%	$30.1024	$30.10	$30.10	$30.10
7 purchase totals =	$1,028.45		$1,114.6325	$1,114.62	$1,114.60	$1,114.60