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	$31.84	4.503%	$33.2738	$33.27	$33.25	$33.30
Purchase #2	$67.31	5.145%	$70.7731	$70.77	$70.75	$70.80
Purchase #3	$6.76	9.586%	$7.408	$7.41	$7.40	$7.40
Purchase #4	$42.60	4.211%	$44.3939	$44.39	$44.40	$44.40
Purchase #5	$78.52	4.741%	$82.2426	$82.24	$82.25	$82.20
Purchase #6	$17.59	4.624%	$18.4034	$18.40	$18.40	$18.40
Purchase #7	$217.76	12.802%	$245.6376	$245.64	$245.65	$245.60
7 purchase totals =	$462.38		$502.1324	$502.12	$502.10	$502.10