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	$195.43	5.154%	$205.5025	$205.50	$205.50	$205.50
Purchase #2	$60.94	7.867%	$65.7341	$65.73	$65.75	$65.70
Purchase #3	$115.60	5.608%	$122.0828	$122.08	$122.10	$122.10
Purchase #4	$97.63	12.262%	$109.6014	$109.60	$109.60	$109.60
Purchase #5	$148.69	7.177%	$159.3615	$159.36	$159.35	$159.40
Purchase #6	$85.48	5.443%	$90.1327	$90.13	$90.15	$90.10
Purchase #7	$94.36	6.152%	$100.165	$100.17	$100.15	$100.20
7 purchase totals =	$798.13		$852.5800	$852.57	$852.60	$852.60