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	$55.73	13.585%	$63.3009	$63.30	$63.30	$63.30
Purchase #2	$22.91	7.601%	$24.6514	$24.65	$24.65	$24.70
Purchase #3	$174.77	12.380%	$196.4065	$196.41	$196.40	$196.40
Purchase #4	$212.55	12.571%	$239.2697	$239.27	$239.25	$239.30
Purchase #5	$115.74	7.372%	$124.2724	$124.27	$124.25	$124.30
Purchase #6	$202.60	9.771%	$222.396	$222.40	$222.40	$222.40
Purchase #7	$196.43	9.663%	$215.411	$215.41	$215.40	$215.40
7 purchase totals =	$980.73		$1,085.7079	$1,085.71	$1,085.65	$1,085.80