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	$188.26	3.314%	$194.4989	$194.50	$194.50	$194.50
Purchase #2	$153.50	3.603%	$159.0306	$159.03	$159.05	$159.00
Purchase #3	$151.32	3.673%	$156.878	$156.88	$156.90	$156.90
Purchase #4	$168.49	13.539%	$191.3019	$191.30	$191.30	$191.30
Purchase #5	$127.69	4.764%	$133.7732	$133.77	$133.75	$133.80
Purchase #6	$16.90	9.269%	$18.4665	$18.47	$18.45	$18.50
Purchase #7	$39.93	6.404%	$42.4871	$42.49	$42.50	$42.50
7 purchase totals =	$846.09		$896.4362	$896.44	$896.45	$896.50