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	$209.66	11.515%	$233.8023	$233.80	$233.80	$233.80
Purchase #2	$172.38	8.219%	$186.5479	$186.55	$186.55	$186.50
Purchase #3	$94.42	12.432%	$106.1583	$106.16	$106.15	$106.20
Purchase #4	$114.72	11.360%	$127.7522	$127.75	$127.75	$127.80
Purchase #5	$176.64	10.740%	$195.6111	$195.61	$195.60	$195.60
Purchase #6	$100.97	8.327%	$109.3778	$109.38	$109.40	$109.40
Purchase #7	$55.49	4.221%	$57.8322	$57.83	$57.85	$57.80
7 purchase totals =	$924.28		$1,017.0818	$1,017.08	$1,017.10	$1,017.10