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	$178.26	10.374%	$196.7527	$196.75	$196.75	$196.80
Purchase #2	$88.88	8.671%	$96.5868	$96.59	$96.60	$96.60
Purchase #3	$179.94	7.868%	$194.0977	$194.10	$194.10	$194.10
Purchase #4	$72.40	12.287%	$81.2958	$81.30	$81.30	$81.30
Purchase #5	$164.41	3.498%	$170.1611	$170.16	$170.15	$170.20
Purchase #6	$70.83	10.623%	$78.3543	$78.35	$78.35	$78.40
Purchase #7	$173.74	12.318%	$195.1413	$195.14	$195.15	$195.10
7 purchase totals =	$928.46		$1,012.3897	$1,012.39	$1,012.40	$1,012.50