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	$204.93	3.796%	$212.7091	$212.71	$212.70	$212.70
Purchase #2	$45.46	12.593%	$51.1848	$51.18	$51.20	$51.20
Purchase #3	$210.79	5.392%	$222.1558	$222.16	$222.15	$222.20
Purchase #4	$113.77	5.780%	$120.3459	$120.35	$120.35	$120.30
Purchase #5	$39.56	12.262%	$44.4108	$44.41	$44.40	$44.40
Purchase #6	$115.62	10.218%	$127.4341	$127.43	$127.45	$127.40
Purchase #7	$219.90	3.515%	$227.6295	$227.63	$227.65	$227.60
7 purchase totals =	$950.03		$1,005.8700	$1,005.87	$1,005.90	$1,005.80