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	$179.64	10.474%	$198.4555	$198.46	$198.45	$198.50
Purchase #2	$57.94	13.315%	$65.6547	$65.65	$65.65	$65.70
Purchase #3	$209.54	6.253%	$222.6425	$222.64	$222.65	$222.60
Purchase #4	$224.54	3.162%	$231.64	$231.64	$231.65	$231.60
Purchase #5	$30.33	11.238%	$33.7385	$33.74	$33.75	$33.70
Purchase #6	$219.29	7.347%	$235.4012	$235.40	$235.40	$235.40
Purchase #7	$88.85	11.494%	$99.0624	$99.06	$99.05	$99.10
7 purchase totals =	$1,010.13		$1,086.5948	$1,086.59	$1,086.60	$1,086.60