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	$144.27	6.788%	$154.063	$154.06	$154.05	$154.10
Purchase #2	$242.29	12.797%	$273.2959	$273.30	$273.30	$273.30
Purchase #3	$31.47	12.663%	$35.455	$35.46	$35.45	$35.50
Purchase #4	$159.31	9.263%	$174.0669	$174.07	$174.05	$174.10
Purchase #5	$184.39	13.570%	$209.4117	$209.41	$209.40	$209.40
Purchase #6	$145.57	4.853%	$152.6345	$152.63	$152.65	$152.60
Purchase #7	$249.83	5.598%	$263.8155	$263.82	$263.80	$263.80
7 purchase totals =	$1,157.13		$1,262.7425	$1,262.75	$1,262.70	$1,262.80