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	$79.63	4.253%	$83.0167	$83.02	$83.00	$83.00
Purchase #2	$85.38	4.520%	$89.2392	$89.24	$89.25	$89.20
Purchase #3	$48.36	13.251%	$54.7682	$54.77	$54.75	$54.80
Purchase #4	$183.87	13.368%	$208.4497	$208.45	$208.45	$208.40
Purchase #5	$174.89	6.219%	$185.7664	$185.77	$185.75	$185.80
Purchase #6	$155.41	3.203%	$160.3878	$160.39	$160.40	$160.40
Purchase #7	$249.75	6.302%	$265.4892	$265.49	$265.50	$265.50
7 purchase totals =	$977.29		$1,047.1172	$1,047.13	$1,047.10	$1,047.10