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	$169.44	12.426%	$190.4946	$190.49	$190.50	$190.50
Purchase #2	$78.27	10.368%	$86.385	$86.39	$86.40	$86.40
Purchase #3	$67.71	6.435%	$72.0671	$72.07	$72.05	$72.10
Purchase #4	$147.75	9.690%	$162.067	$162.07	$162.05	$162.10
Purchase #5	$244.48	3.224%	$252.362	$252.36	$252.35	$252.40
Purchase #6	$169.98	9.209%	$185.6335	$185.63	$185.65	$185.60
Purchase #7	$72.35	6.725%	$77.2155	$77.22	$77.20	$77.20
7 purchase totals =	$949.98		$1,026.2247	$1,026.23	$1,026.20	$1,026.30