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	$98.66	6.711%	$105.2811	$105.28	$105.30	$105.30
Purchase #2	$183.88	11.616%	$205.2395	$205.24	$205.25	$205.20
Purchase #3	$94.54	9.521%	$103.5412	$103.54	$103.55	$103.50
Purchase #4	$169.66	11.272%	$188.7841	$188.78	$188.80	$188.80
Purchase #5	$211.88	4.483%	$221.3786	$221.38	$221.40	$221.40
Purchase #6	$232.71	3.194%	$240.1428	$240.14	$240.15	$240.10
Purchase #7	$211.70	12.833%	$238.8675	$238.87	$238.85	$238.90
7 purchase totals =	$1,203.03		$1,303.2348	$1,303.23	$1,303.30	$1,303.20