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	$213.38	13.546%	$242.2845	$242.28	$242.30	$242.30
Purchase #2	$152.41	8.642%	$165.5813	$165.58	$165.60	$165.60
Purchase #3	$98.47	5.219%	$103.6091	$103.61	$103.60	$103.60
Purchase #4	$115.88	9.171%	$126.5074	$126.51	$126.50	$126.50
Purchase #5	$194.54	6.543%	$207.2688	$207.27	$207.25	$207.30
Purchase #6	$31.94	12.432%	$35.9108	$35.91	$35.90	$35.90
Purchase #7	$165.64	5.223%	$174.2914	$174.29	$174.30	$174.30
7 purchase totals =	$972.26		$1,055.4533	$1,055.45	$1,055.45	$1,055.50