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	$100.76	4.307%	$105.0997	$105.10	$105.10	$105.10
Purchase #2	$198.26	7.129%	$212.394	$212.39	$212.40	$212.40
Purchase #3	$152.30	4.621%	$159.3378	$159.34	$159.35	$159.30
Purchase #4	$90.41	7.829%	$97.4882	$97.49	$97.50	$97.50
Purchase #5	$36.54	10.470%	$40.3657	$40.37	$40.35	$40.40
Purchase #6	$152.45	10.280%	$168.1219	$168.12	$168.10	$168.10
Purchase #7	$101.77	12.483%	$114.4739	$114.47	$114.45	$114.50
7 purchase totals =	$832.49		$897.2812	$897.28	$897.25	$897.30