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	$106.91	6.749%	$114.1254	$114.13	$114.15	$114.10
Purchase #2	$88.44	3.425%	$91.4691	$91.47	$91.45	$91.50
Purchase #3	$189.70	4.632%	$198.4869	$198.49	$198.50	$198.50
Purchase #4	$198.43	12.550%	$223.333	$223.33	$223.35	$223.30
Purchase #5	$51.90	7.677%	$55.8844	$55.88	$55.90	$55.90
Purchase #6	$84.58	6.752%	$90.2908	$90.29	$90.30	$90.30
Purchase #7	$16.81	3.658%	$17.4249	$17.42	$17.40	$17.40
7 purchase totals =	$736.77		$791.0145	$791.01	$791.05	$791.00