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	$178.42	11.185%	$198.3763	$198.38	$198.40	$198.40
Purchase #2	$64.99	11.554%	$72.4989	$72.50	$72.50	$72.50
Purchase #3	$163.34	3.180%	$168.5342	$168.53	$168.55	$168.50
Purchase #4	$246.68	11.793%	$275.771	$275.77	$275.75	$275.80
Purchase #5	$103.48	8.326%	$112.0957	$112.10	$112.10	$112.10
Purchase #6	$102.57	6.578%	$109.3171	$109.32	$109.30	$109.30
Purchase #7	$91.55	6.451%	$97.4559	$97.46	$97.45	$97.50
7 purchase totals =	$951.03		$1,034.0491	$1,034.06	$1,034.05	$1,034.10