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	$90.78	11.803%	$101.4948	$101.49	$101.50	$101.50
Purchase #2	$128.83	10.657%	$142.5594	$142.56	$142.55	$142.60
Purchase #3	$163.38	6.467%	$173.9458	$173.95	$173.95	$173.90
Purchase #4	$78.26	6.186%	$83.1012	$83.10	$83.10	$83.10
Purchase #5	$249.58	7.142%	$267.405	$267.41	$267.40	$267.40
Purchase #6	$168.45	7.425%	$180.9574	$180.96	$180.95	$181.00
Purchase #7	$100.45	3.819%	$104.2862	$104.29	$104.30	$104.30
7 purchase totals =	$979.73		$1,053.7498	$1,053.76	$1,053.75	$1,053.80