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	$197.34	6.873%	$210.9032	$210.90	$210.90	$210.90
Purchase #2	$34.45	9.204%	$37.6208	$37.62	$37.60	$37.60
Purchase #3	$183.36	11.599%	$204.6279	$204.63	$204.65	$204.60
Purchase #4	$62.70	12.611%	$70.6071	$70.61	$70.60	$70.60
Purchase #5	$71.27	9.620%	$78.1262	$78.13	$78.15	$78.10
Purchase #6	$52.49	6.508%	$55.906	$55.91	$55.90	$55.90
Purchase #7	$105.30	9.818%	$115.6384	$115.64	$115.65	$115.60
7 purchase totals =	$706.91		$773.4296	$773.44	$773.45	$773.30