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	$100.56	3.569%	$104.149	$104.15	$104.15	$104.10
Purchase #2	$245.90	3.316%	$254.054	$254.05	$254.05	$254.10
Purchase #3	$110.30	4.245%	$114.9822	$114.98	$115.00	$115.00
Purchase #4	$35.60	3.404%	$36.8118	$36.81	$36.80	$36.80
Purchase #5	$68.46	6.506%	$72.914	$72.91	$72.90	$72.90
Purchase #6	$92.54	8.344%	$100.2615	$100.26	$100.25	$100.30
Purchase #7	$205.94	8.423%	$223.2863	$223.29	$223.30	$223.30
7 purchase totals =	$859.30		$906.4588	$906.45	$906.45	$906.50