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	$211.57	8.661%	$229.8941	$229.89	$229.90	$229.90
Purchase #2	$187.64	11.683%	$209.562	$209.56	$209.55	$209.60
Purchase #3	$213.82	6.648%	$228.0348	$228.03	$228.05	$228.00
Purchase #4	$205.53	7.673%	$221.3003	$221.30	$221.30	$221.30
Purchase #5	$243.71	7.671%	$262.405	$262.41	$262.40	$262.40
Purchase #6	$47.43	13.495%	$53.8307	$53.83	$53.85	$53.80
Purchase #7	$173.65	4.199%	$180.9416	$180.94	$180.95	$180.90
7 purchase totals =	$1,283.35		$1,385.9685	$1,385.96	$1,386.00	$1,385.90