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	$73.25	11.831%	$81.9162	$81.92	$81.90	$81.90
Purchase #2	$92.33	11.645%	$103.0818	$103.08	$103.10	$103.10
Purchase #3	$201.56	5.303%	$212.2487	$212.25	$212.25	$212.20
Purchase #4	$80.80	11.298%	$89.9288	$89.93	$89.95	$89.90
Purchase #5	$89.36	6.703%	$95.3498	$95.35	$95.35	$95.30
Purchase #6	$243.87	9.240%	$266.4036	$266.40	$266.40	$266.40
Purchase #7	$93.32	6.407%	$99.299	$99.30	$99.30	$99.30
7 purchase totals =	$874.49		$948.2279	$948.23	$948.25	$948.10