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	$88.88	6.216%	$94.4048	$94.40	$94.40	$94.40
Purchase #2	$77.42	6.213%	$82.2301	$82.23	$82.25	$82.20
Purchase #3	$219.89	6.731%	$234.6908	$234.69	$234.70	$234.70
Purchase #4	$157.89	7.456%	$169.6623	$169.66	$169.65	$169.70
Purchase #5	$139.82	5.305%	$147.2375	$147.24	$147.25	$147.20
Purchase #6	$162.42	7.815%	$175.1131	$175.11	$175.10	$175.10
Purchase #7	$229.98	5.462%	$242.5415	$242.54	$242.55	$242.50
7 purchase totals =	$1,076.30		$1,145.8801	$1,145.87	$1,145.90	$1,145.80