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	$115.86	13.185%	$131.1361	$131.14	$131.15	$131.10
Purchase #2	$216.94	10.107%	$238.8661	$238.87	$238.85	$238.90
Purchase #3	$88.42	3.788%	$91.7693	$91.77	$91.75	$91.80
Purchase #4	$201.49	4.170%	$209.8921	$209.89	$209.90	$209.90
Purchase #5	$145.89	6.391%	$155.2138	$155.21	$155.20	$155.20
Purchase #6	$149.85	6.343%	$159.355	$159.36	$159.35	$159.40
Purchase #7	$82.66	9.363%	$90.3995	$90.40	$90.40	$90.40
7 purchase totals =	$1,001.11		$1,076.6319	$1,076.64	$1,076.60	$1,076.70