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	$97.88	8.438%	$106.1391	$106.14	$106.15	$106.10
Purchase #2	$38.73	8.272%	$41.9337	$41.93	$41.95	$41.90
Purchase #3	$39.27	8.648%	$42.6661	$42.67	$42.65	$42.70
Purchase #4	$215.50	8.729%	$234.311	$234.31	$234.30	$234.30
Purchase #5	$229.65	11.223%	$255.4236	$255.42	$255.40	$255.40
Purchase #6	$31.41	3.661%	$32.5599	$32.56	$32.55	$32.60
Purchase #7	$75.97	5.861%	$80.4226	$80.42	$80.40	$80.40
7 purchase totals =	$728.41		$793.4560	$793.45	$793.40	$793.40