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	$129.65	8.871%	$141.1513	$141.15	$141.15	$141.20
Purchase #2	$136.87	4.251%	$142.6883	$142.69	$142.70	$142.70
Purchase #3	$175.57	5.608%	$185.416	$185.42	$185.40	$185.40
Purchase #4	$100.41	6.334%	$106.77	$106.77	$106.75	$106.80
Purchase #5	$210.73	10.574%	$233.0126	$233.01	$233.00	$233.00
Purchase #6	$160.93	11.343%	$179.1843	$179.18	$179.20	$179.20
Purchase #7	$12.77	7.223%	$13.6924	$13.69	$13.70	$13.70
7 purchase totals =	$926.93		$1,001.9149	$1,001.91	$1,001.90	$1,002.00