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	$18.51	5.104%	$19.4548	$19.45	$19.45	$19.50
Purchase #2	$101.90	10.482%	$112.5812	$112.58	$112.60	$112.60
Purchase #3	$95.70	4.675%	$100.174	$100.17	$100.15	$100.20
Purchase #4	$209.79	9.440%	$229.5942	$229.59	$229.60	$229.60
Purchase #5	$123.99	5.215%	$130.4561	$130.46	$130.45	$130.50
Purchase #6	$164.94	3.714%	$171.0659	$171.07	$171.05	$171.10
Purchase #7	$159.68	5.282%	$168.1143	$168.11	$168.10	$168.10
7 purchase totals =	$874.51		$931.4405	$931.43	$931.40	$931.60