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	$220.98	3.536%	$228.7939	$228.79	$228.80	$228.80
Purchase #2	$191.69	12.752%	$216.1343	$216.13	$216.15	$216.10
Purchase #3	$60.31	8.385%	$65.367	$65.37	$65.35	$65.40
Purchase #4	$118.27	12.707%	$133.2986	$133.30	$133.30	$133.30
Purchase #5	$95.55	4.818%	$100.1536	$100.15	$100.15	$100.20
Purchase #6	$100.59	3.598%	$104.2092	$104.21	$104.20	$104.20
Purchase #7	$194.56	13.333%	$220.5007	$220.50	$220.50	$220.50
7 purchase totals =	$981.95		$1,068.4573	$1,068.45	$1,068.45	$1,068.50