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	$196.43	13.185%	$222.3293	$222.33	$222.35	$222.30
Purchase #2	$184.70	6.186%	$196.1255	$196.13	$196.15	$196.10
Purchase #3	$170.90	13.748%	$194.3953	$194.40	$194.40	$194.40
Purchase #4	$209.42	12.253%	$235.0802	$235.08	$235.10	$235.10
Purchase #5	$93.95	12.450%	$105.6468	$105.65	$105.65	$105.60
Purchase #6	$16.69	12.418%	$18.7626	$18.76	$18.75	$18.80
Purchase #7	$73.49	7.522%	$79.0179	$79.02	$79.00	$79.00
7 purchase totals =	$945.58		$1,051.3576	$1,051.37	$1,051.40	$1,051.30