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	$183.45	5.801%	$194.0919	$194.09	$194.10	$194.10
Purchase #2	$17.49	12.635%	$19.6999	$19.70	$19.70	$19.70
Purchase #3	$142.62	12.112%	$159.8941	$159.89	$159.90	$159.90
Purchase #4	$133.78	6.336%	$142.2563	$142.26	$142.25	$142.30
Purchase #5	$96.58	10.257%	$106.4862	$106.49	$106.50	$106.50
Purchase #6	$213.30	4.123%	$222.0944	$222.09	$222.10	$222.10
Purchase #7	$212.42	4.474%	$221.9237	$221.92	$221.90	$221.90
7 purchase totals =	$999.64		$1,066.4465	$1,066.44	$1,066.45	$1,066.50