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	$168.64	6.329%	$179.3132	$179.31	$179.30	$179.30
Purchase #2	$209.94	11.274%	$233.6086	$233.61	$233.60	$233.60
Purchase #3	$64.76	13.786%	$73.6878	$73.69	$73.70	$73.70
Purchase #4	$142.97	5.713%	$151.1379	$151.14	$151.15	$151.10
Purchase #5	$134.74	13.108%	$152.4017	$152.40	$152.40	$152.40
Purchase #6	$158.56	7.112%	$169.8368	$169.84	$169.85	$169.80
Purchase #7	$37.95	8.388%	$41.1332	$41.13	$41.15	$41.10
7 purchase totals =	$917.56		$1,001.1192	$1,001.12	$1,001.15	$1,001.00