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	$194.86	4.844%	$204.299	$204.30	$204.30	$204.30
Purchase #2	$234.88	3.633%	$243.4132	$243.41	$243.40	$243.40
Purchase #3	$95.39	5.637%	$100.7671	$100.77	$100.75	$100.80
Purchase #4	$109.89	11.612%	$122.6504	$122.65	$122.65	$122.70
Purchase #5	$96.56	9.642%	$105.8703	$105.87	$105.85	$105.90
Purchase #6	$191.43	4.402%	$199.8567	$199.86	$199.85	$199.90
Purchase #7	$172.27	11.554%	$192.1741	$192.17	$192.15	$192.20
7 purchase totals =	$1,095.28		$1,169.0308	$1,169.03	$1,168.95	$1,169.20