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	$172.40	9.622%	$188.9883	$188.99	$189.00	$189.00
Purchase #2	$219.88	6.441%	$234.0425	$234.04	$234.05	$234.00
Purchase #3	$161.76	4.340%	$168.7804	$168.78	$168.80	$168.80
Purchase #4	$65.27	8.663%	$70.9243	$70.92	$70.90	$70.90
Purchase #5	$79.79	8.277%	$86.3942	$86.39	$86.40	$86.40
Purchase #6	$80.71	10.427%	$89.1256	$89.13	$89.15	$89.10
Purchase #7	$219.44	12.662%	$247.2255	$247.23	$247.25	$247.20
7 purchase totals =	$999.25		$1,085.4808	$1,085.48	$1,085.55	$1,085.40