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	$96.90	8.172%	$104.8187	$104.82	$104.80	$104.80
Purchase #2	$219.54	10.285%	$242.1197	$242.12	$242.10	$242.10
Purchase #3	$117.27	8.814%	$127.6062	$127.61	$127.60	$127.60
Purchase #4	$68.56	12.424%	$77.0779	$77.08	$77.10	$77.10
Purchase #5	$72.41	13.692%	$82.3244	$82.32	$82.30	$82.30
Purchase #6	$170.65	7.551%	$183.5358	$183.54	$183.55	$183.50
Purchase #7	$245.91	12.509%	$276.6709	$276.67	$276.65	$276.70
7 purchase totals =	$991.24		$1,094.1536	$1,094.16	$1,094.10	$1,094.10