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	$174.37	10.159%	$192.0842	$192.08	$192.10	$192.10
Purchase #2	$158.67	5.592%	$167.5428	$167.54	$167.55	$167.50
Purchase #3	$25.53	6.231%	$27.1208	$27.12	$27.10	$27.10
Purchase #4	$156.38	7.804%	$168.5839	$168.58	$168.60	$168.60
Purchase #5	$156.79	12.165%	$175.8635	$175.86	$175.85	$175.90
Purchase #6	$90.59	10.567%	$100.1626	$100.16	$100.15	$100.20
Purchase #7	$22.67	13.518%	$25.7345	$25.73	$25.75	$25.70
7 purchase totals =	$785.00		$857.0923	$857.07	$857.10	$857.10