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	$180.90	5.640%	$191.1028	$191.10	$191.10	$191.10
Purchase #2	$244.99	12.632%	$275.9371	$275.94	$275.95	$275.90
Purchase #3	$47.31	12.153%	$53.0596	$53.06	$53.05	$53.10
Purchase #4	$113.75	8.628%	$123.5644	$123.56	$123.55	$123.60
Purchase #5	$27.69	3.517%	$28.6639	$28.66	$28.65	$28.70
Purchase #6	$100.55	9.504%	$110.1063	$110.11	$110.10	$110.10
Purchase #7	$50.30	6.151%	$53.394	$53.39	$53.40	$53.40
7 purchase totals =	$765.49		$835.8281	$835.82	$835.80	$835.90