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	$180.98	5.443%	$190.8307	$190.83	$190.85	$190.80
Purchase #2	$75.72	8.422%	$82.0971	$82.10	$82.10	$82.10
Purchase #3	$92.63	4.187%	$96.5084	$96.51	$96.50	$96.50
Purchase #4	$127.66	13.473%	$144.8596	$144.86	$144.85	$144.90
Purchase #5	$221.36	3.181%	$228.4015	$228.40	$228.40	$228.40
Purchase #6	$103.73	6.813%	$110.7971	$110.80	$110.80	$110.80
Purchase #7	$43.75	6.147%	$46.4393	$46.44	$46.45	$46.40
7 purchase totals =	$845.83		$899.9337	$899.94	$899.95	$899.90