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	$185.94	4.745%	$194.7629	$194.76	$194.75	$194.80
Purchase #2	$84.29	3.293%	$87.0657	$87.07	$87.05	$87.10
Purchase #3	$79.58	12.539%	$89.5585	$89.56	$89.55	$89.60
Purchase #4	$152.66	4.843%	$160.0533	$160.05	$160.05	$160.10
Purchase #5	$99.70	3.315%	$103.0051	$103.01	$103.00	$103.00
Purchase #6	$145.84	3.831%	$151.4271	$151.43	$151.45	$151.40
Purchase #7	$249.71	5.447%	$263.3117	$263.31	$263.30	$263.30
7 purchase totals =	$997.72		$1,049.1843	$1,049.19	$1,049.15	$1,049.30