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	$67.32	3.105%	$69.4103	$69.41	$69.40	$69.40
Purchase #2	$115.69	9.574%	$126.7662	$126.77	$126.75	$126.80
Purchase #3	$115.38	4.661%	$120.7579	$120.76	$120.75	$120.80
Purchase #4	$57.35	5.498%	$60.5031	$60.50	$60.50	$60.50
Purchase #5	$118.37	7.564%	$127.3235	$127.32	$127.30	$127.30
Purchase #6	$31.90	4.776%	$33.4235	$33.42	$33.40	$33.40
Purchase #7	$180.45	3.585%	$186.9191	$186.92	$186.90	$186.90
7 purchase totals =	$686.46		$725.1036	$725.10	$725.00	$725.10