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	$202.88	9.735%	$222.6304	$222.63	$222.65	$222.60
Purchase #2	$51.27	7.331%	$55.0286	$55.03	$55.05	$55.00
Purchase #3	$178.42	11.523%	$198.9793	$198.98	$199.00	$199.00
Purchase #4	$105.57	5.414%	$111.2856	$111.29	$111.30	$111.30
Purchase #5	$193.88	11.302%	$215.7923	$215.79	$215.80	$215.80
Purchase #6	$190.28	9.862%	$209.0454	$209.05	$209.05	$209.00
Purchase #7	$169.72	5.475%	$179.0122	$179.01	$179.00	$179.00
7 purchase totals =	$1,092.02		$1,191.7738	$1,191.78	$1,191.85	$1,191.70