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	$33.61	10.193%	$37.0359	$37.04	$37.05	$37.00
Purchase #2	$249.76	7.814%	$269.2762	$269.28	$269.30	$269.30
Purchase #3	$49.88	4.499%	$52.1241	$52.12	$52.10	$52.10
Purchase #4	$218.37	6.732%	$233.0707	$233.07	$233.05	$233.10
Purchase #5	$105.36	13.734%	$119.8301	$119.83	$119.85	$119.80
Purchase #6	$191.28	6.721%	$204.1359	$204.14	$204.15	$204.10
Purchase #7	$212.31	8.156%	$229.626	$229.63	$229.65	$229.60
7 purchase totals =	$1,060.57		$1,145.0989	$1,145.11	$1,145.15	$1,145.00