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	$179.68	3.219%	$185.4639	$185.46	$185.45	$185.50
Purchase #2	$78.79	12.419%	$88.5749	$88.57	$88.55	$88.60
Purchase #3	$233.62	6.116%	$247.9082	$247.91	$247.90	$247.90
Purchase #4	$244.98	6.779%	$261.5872	$261.59	$261.60	$261.60
Purchase #5	$245.61	10.778%	$272.0818	$272.08	$272.10	$272.10
Purchase #6	$41.79	8.423%	$45.31	$45.31	$45.30	$45.30
Purchase #7	$25.56	6.128%	$27.1263	$27.13	$27.15	$27.10
7 purchase totals =	$1,050.03		$1,128.0523	$1,128.05	$1,128.05	$1,128.10