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	$109.43	5.461%	$115.406	$115.41	$115.40	$115.40
Purchase #2	$119.61	4.228%	$124.6671	$124.67	$124.65	$124.70
Purchase #3	$80.77	3.146%	$83.311	$83.31	$83.30	$83.30
Purchase #4	$104.78	11.199%	$116.5143	$116.51	$116.50	$116.50
Purchase #5	$147.73	6.316%	$157.0606	$157.06	$157.05	$157.10
Purchase #6	$75.53	12.663%	$85.0944	$85.09	$85.10	$85.10
Purchase #7	$118.36	7.538%	$127.282	$127.28	$127.30	$127.30
7 purchase totals =	$756.21		$809.3354	$809.33	$809.30	$809.40