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	$229.69	6.564%	$244.7669	$244.77	$244.75	$244.80
Purchase #2	$105.74	13.394%	$119.9028	$119.90	$119.90	$119.90
Purchase #3	$51.83	3.429%	$53.6073	$53.61	$53.60	$53.60
Purchase #4	$235.40	4.349%	$245.6375	$245.64	$245.65	$245.60
Purchase #5	$156.94	7.745%	$169.095	$169.10	$169.10	$169.10
Purchase #6	$63.46	3.561%	$65.7198	$65.72	$65.70	$65.70
Purchase #7	$105.56	3.426%	$109.1765	$109.18	$109.20	$109.20
7 purchase totals =	$948.62		$1,007.9058	$1,007.92	$1,007.90	$1,007.90