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	$91.79	12.510%	$103.2729	$103.27	$103.25	$103.30
Purchase #2	$239.40	4.824%	$250.9487	$250.95	$250.95	$250.90
Purchase #3	$91.85	13.294%	$104.0605	$104.06	$104.05	$104.10
Purchase #4	$59.93	9.412%	$65.5706	$65.57	$65.55	$65.60
Purchase #5	$144.91	3.109%	$149.4153	$149.42	$149.40	$149.40
Purchase #6	$96.26	4.404%	$100.4993	$100.50	$100.50	$100.50
Purchase #7	$233.37	8.436%	$253.0571	$253.06	$253.05	$253.10
7 purchase totals =	$957.51		$1,026.8244	$1,026.83	$1,026.75	$1,026.90