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	$67.79	9.289%	$74.087	$74.09	$74.10	$74.10
Purchase #2	$239.65	6.125%	$254.3286	$254.33	$254.35	$254.30
Purchase #3	$203.43	6.402%	$216.4536	$216.45	$216.45	$216.50
Purchase #4	$39.88	7.562%	$42.8957	$42.90	$42.90	$42.90
Purchase #5	$137.69	12.152%	$154.4221	$154.42	$154.40	$154.40
Purchase #6	$160.56	12.112%	$180.007	$180.01	$180.00	$180.00
Purchase #7	$153.33	9.616%	$168.0742	$168.07	$168.05	$168.10
7 purchase totals =	$1,002.33		$1,090.2682	$1,090.27	$1,090.25	$1,090.30